The present invention refers to a method of testing the position of an edit point or cut between a magnetic tape impressed with a recording and packed in a cassette (MC or DCC) and a leader spliced ahead of the recording or a trailer spliced after the recording through playback of the cassette and determination of the distance of the edit point from either a cue tone located at least before the beginning of the recording or from the beginning of the recording, or from a cue tone located at least behind the end of the recording or from the end of the recording, with the magnetic tape being played back for conducting the testing operation at standard speed normal for magnetic tape cassettes. The present invention refers also to an apparatus for carrying out this method.
For reproducing analogous or digital data information, such as for example music scores, on magnetic tape cassettes, the information is recorded initially in multiple sequence onto a long tape wound on a supply reel (tape pancake). Thus, each duplicated tape pancake contains a series of copy recordings of a master, separated by the 6Hz cue tone. The pauses between identical successive recordings are of a same length, however, may vary from manufacturer to manufacturer between about 10 to 20 seconds. The length of the supply reel ranges between about 3,500 to 7,020 m, with a cue tone being recorded in the pauses between successive recordings. By means of the recorded cue tone, the tape machine used for packing the tape pancake into the empty cassette shells sets the edit point between identical recordings upon the supply reel.
Four different positions designated I, II, III or IV are currently utilized during production of recorded magnetic tape cassettes for impressing the cue tone with variable distance to the recorded data information. In analog as well as digital recording, the tape is split in two halves (A-side and B-side) which upon recordation in analog fashion includes two tracks, and upon recordation in digital fashion includes nine tracks. The A-side and the B-side are recorded and played back in opposite tape travel directions, with the cue tone being impressed over the entire width of the respective A-side or B side i.e. on both tracks at analogous recordation, or on all nine tracks at digital recordation. At standard speed, i.e. 4.76 cm/s of the magnetic tape, the frequency of the cue tone is 6 Hz. The timed length of the recorded cue tone amounts at the standard speed of 4.76 cm/s typically to between about 2 and 3 seconds. The position I for the recorded cue tone is located on the B-side before the beginning of the B-side. The position II for the recorded cue tone, as used during production of DCC, is situated on the A-side before its end. In the position III, the recorded cue tone is recorded on the A-side before its beginning and in the position IV, the cue tone is recorded on the B-side before its end.
In general, cassettes packed with edited magnetic tapes are controlled by a tester through randomly picking samples from a plurality of cassettes made in the tailoring and winding machine. These randomly picked samples are checked in the area of the recorded cue tone as to whether the edit point or cut with the leader or trailer is outside the recording or within the recording. Until an error can be detected in this manner, the entire edited batch (about 2,000 to 5,000 magnetic tape cassettes) is generally processed so that the entire production cannot be shipped when an editing error is detected. Theoretically, the ensuing high reject rate during production of recorded magnetic tape cassettes could be reduced by increasing the number of testing personnel and tape machines to enable an error detection during packing edited tapes into empty cassettes before the production end. However, the testing operation becomes prohibitively expensive and uneconomical.